RV Electricity – Tighten those transfer switch terminals carefully

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By Mike Sokol 

Dear Mike,
Saw your seminar in Goshen at the Heartland Rally, and it was really informative. Can you go into more detail on how to properly tighten the terminal screws in a generator transfer switch without breaking them off? Thanks. —Billy D

Dear Billy,
Certainly. First I’ll do a little overview of why these screws always seem to work loose, and go over the tightening procedure. I’ll include a video from my Advanced RV Electricity Seminar I did in Funkstown, MD, on June 8th.

First of all, I’m a firm believer that most overheated wiring situations in transfer switches are due to loose screws in the terminal connections on the contactor/relays. This is simply due to road vibration and heating/cooling cycles, none of which these electrical components would normally experience in a home wiring situation.

So what are we to do? Well, start with a yearly maintenance schedule where you re-torque all the wiring terminals in your transfer switch, inverter/converter connection and circuit breakers. It’s also a good idea to test the screws in your RV’s shore power inlet, as well as inspecting everything for any signs of overheating or physical damage.

Now, as I hinted at in my RVelectricity seminar, you don’t want to simply get wrenching down on these wiring terminals as it’s pretty easy to break off the insulating tab. What you need to do is determine the actual in/lbs of torque recommended by the manufacturer. Note that I said INCH/POUNDS not FOOT/POUNDS. You torque lug nuts on your wheels to maybe 75 to 125 ft/lbs, but electrical terminals on relays and inverters are typically more like 25 or 35 INCH/LBS.

I’m a big believer in using the right tool for the job, so a variable torque screwdriver that “breaks” at the desired torque (not just clicks) is what’s needed. Here’s what I used in my video, which is a little too expensive for casual users but not too much for a professional RV technician or shop.

First of all, before you start sticking metal objects in anything with wire, make sure all power is off. That is, your RV needs to be disconnected from shore power, generator power and inverter power.

Next, determine the proper amount of torque needed for each terminal connection. On the Southwire transfer switch I’m showing, the screw terminals require 35 in/lbs of torque. So set your screwdriver to the proper amount of twisting action as specified.

Now back the screw out a quarter turn to make sure it’s free of any rust or spalling that would lock up a loose screw.

Proceed to tighten the screw normally until the torque limiting screwdriver “clicks” and breaks at the correct amount of torque. “Rinse and repeat” until you’ve covered all of the screws in the panel.

While you’re at it, carefully inspect all wiring and connectors for any signs of damage, either due to the insulation being overheated or cut, or wiring strands hanging out of the screw terminal.

BTW: Here’s the less expensive version of my commercial duty torque screwdriver that should work just fine for your terminal tightening jobs. You can purchase it on Amazon HERE.

That’s it. You’ve eliminated a lot of potential failure points during your next trip so you can enjoy more camping time with friends and family. Plus, you’ve increased the safety of your RV’s electrical system, which is most important of all.

More on this later, but in the meantime – let’s play safe out there….

 

Mike Sokol is an electrical and professional sound expert with 40+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.

##RVT904

 

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Gene Bjerke
5 months ago

Mike, I have a question and I don’t know how else to get in touch with you:
I drive a Class B on a Sprinter chassis. Sometimes when I plug in, my surge protector (SurgeGuard #34730) indicates a reversed polarity condition. It passes the power through anyway, and I go ahead and use it. So far, there don’t seem to be any problems. Is this a bad thing?
If it is something I should be worried about, could I solve the problem by making a short jumper cord with the wires crossed between the hot and neutral of the female and male ends?
You may have commented on this before, but I can’t find it if you did. Thanks for any information on this.

Jeff
5 months ago

Remember to return the Tool back to its lowest setting, so the tool spring is under constant tension!

Dave Telenko
11 months ago

Thanks Mike, what a great suggestion to first back out the screw 1/4 turn to make sure it’s not frozen in place from corrosion or rust. I was checking out a breaker in my panel & was taking it out & the screws were so tight that I almost stripped the head of the screw off trying to unloosen it Seems the factory installer didn’t have one of those torque drivers! Most likely was using a impact driver! LOL
Dave

Diane Mc
11 months ago

We learned this the hard way. Last trip smelled smoke & it was the ATS. Fortunately found a mobile tech company whose owner’s expertise was electrical. So told us about the loose screws & doing annual check & torquing to proper tightness. I just about everything motorhome, even technical stuff. Drive my husband crazy. But I’ve saved us on a number of things. However, I hadn’t seen anything, that I remember on this issue, until something in an RV Forum & this article. Sending to my husband. A side note, our MH is 17 years old, so ATS lasted pretty long. Grateful the breaker tripped, same time I smelled the smoke smell my husband couldn’t!

Joe Bulger
11 months ago

Good information Mike. It is my experience to check all connections anytime I get into a electrical panel with stranded wire. Let’s not forget that the breaker panel and other electrical equipment also has stranded wiring that can work loose.

Mike Sokol
11 months ago
Reply to  Joe Bulger

Yes, loose screws is probably the main reason for many transfer switches and breaker panels burning up wiring. There is just so much vibration and heat/cooling cycles that the wiring in your bricks and sticks house never go through. Another thing I’ve found is that many times the stranded wires are “tinned” with solder to make installation easier for builders. However, the solder in tinned wires will change dimension under compression, and loosen up on their own, even without the terminal screw loosening up. That’s why we don’t allow tinned/stranded electrical wiring in compression termination fittings. They nearly always loosen up in a few years.